Technical Field
Exemplary aspects of the present disclosure generally relate to an optical system and an imaging device incorporating the optical system.
Related Art
An imaging system including a plurality of wide angle lenses is known, in which the respective wide angle lenses form subject images with the peripheral portions of the respective images overlapping each other, thereby joining the subject images together to obtain a wide view image. Such an imaging system is used in a spherical imaging system, for example.
Wide angle lenses, which are also called fish-eye lenses, have four projection methods, such as an orthogonal projection, an equisolid angle projection, an equidistance projection, and a stereographic projection. The orthogonal projection and equisolid angle projection have been widely adopted in fish eye lenses for silver salt cameras. The stereographic projection is suitable for recent digital cameras to improve resolutions in the peripheral portions accompanying advance in image processing technology. In addition, to achieve a good balance between axial and off-axial resolutions, the equidistance projection is suitably applied. In such cases, however, one fish-eye lens is used alone, unlike in the spherical imaging system described above that includes a plurality of fish-eye lenses combined.